164 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



of the formations in unison with the correlations and nomenclature of 

 neighboring* States. 



In Mr. Safford's 1 report the upper Paleozoic terrane of Tenuessee is 

 sharply denned above aud below. It rests, with very slight uncon- 

 formity, but with unmistakable interval, upon Upper or Lower Silurian 

 rocks, and is capped, with more distinct interval, by the Cretaceous or 

 later rocks. The classification proposed by the author is as follows: 



10. Cretaceous. 



( Upper Coal Measures. 



9. Coal Measures ^ Conglomerate. 



( Lower Coal Measures. 



8. Lower Carboniferous J Mountain limestone. 



} Siliceous group. 

 7. Black shale. 



Silurian — either "6. Lower Helderberg; 5. Meniscus limestone, Dyestone group ; 



or 4. Nashville," as the case may be, etc. 



The lowest member of this upper Paleozoic terrane is the "black 

 shale," a bituminous black shale with grains or nodules of pyrite, 

 which is widely distributed, and, whenever present, is a valuable strati- 

 graphic bench mark. In the eastern part of the State it rests on the 

 "Nashville, or Dyestone, or Meniscus formation;" farther west, on the 

 opposite side of the central basin, the subjacent formation is "Meniscus, 

 Dyestone, or Lower Helderberg." West of the Cumberland tableland 

 it is not solely a black shale; it thins on going westward, and at its top, 

 in a lighter colored shale, is a thin layer of argillaceous fetid concre- 

 tionary bodies called " Kidneys," and taking the place of the lower layer 

 is a stratum varying from 1 to 15 feet of dark gray fetid sandstone, con- 

 taining the same IAngula seen in the typical black shale. This charac- 

 ter of the formation is seen in Wayne and Hardin Counties. The 

 author considered this to be the equivalent of the Devonian, and par- 

 ticularly of the Genesee shale of the Hamilton Period of New York. a 

 The highest rocks seen underlying this were referred to the Lower 

 Helderberg division of the Upper Silurian. The black shale through- 

 out the book is spoken of under this name and not as Devonian. The 

 black shale formation is in some places associated with a sandstone 

 layer containing the same Lingula, varying from a few inches to 15 

 feet. (Wayne County.) 3 Above the black shale is also seen in places 

 a layer of "kidney concretions." It is defined as "a thin layer of 

 argillaceous, very fetid, concretionary bodies called * kidneys. 7 " They 

 are in a bluish shale and vary in size from an inch or less to 2 feet in 

 diameter. In the more eastern sections this black shale rests on the 

 "Nashville" (Sumner County) "Niagara or Dyestone group" (De Kalb 

 and Maury Counties) ; farther west, on the " Meniscus limestone" or Hel- 

 derberg (Wayne and Hardin Counties). Wherever it occurs it is over- 

 lain by the "Siliceous group," or else is the top rock. The place of 

 unconformity is thus shown to be below the black shale formation. 



1 Geology of Tennessee, by James M. Safford, State geologist, Nashville, 1869. 

 8 Ibid., p. 157. 

 * Ibid., p. 331. 



